Photocatalytically active titanium oxide is applied in a broad range of areas because titanium oxide is a material with anti-staining/fouling, anti-bacterial and odor eliminating properties, upon radiation by sun light or ultra-violet light. Photocatlytic titanium oxide is usually made of spherical microparticles in the range of a few nm to several tens of nm. When photocatlytic titanium oxide is used for a film, as shown in FIG. 3, spherical microparticles of titanium oxide P5 are fixed on a base material P1 by using a suitable fixing agent P3 which is called a binder. In this way, photocatlytic titanium is used as a coating agent. material. The binder is selected depending on a type of the base material to be coated. Inorganic binder, such as silica or silicate, or organic binder, such as silicone resin or fluorine resin, which are resistant to the photocatalytic reaction, are used. Another method is also known wherein titanium oxide sol obtained from hydrolyzing titanium tetra alkoxide, such as Ti(OC3H7)4, is used as a coating agent.
Titanium oxide is also used in the form of sol solution wherein sheet-like microparticles of titanium oxide (titanium oxide nanosheets) are dispersed. This sol solution can be obtained by acidifying titanate compound having a layer structure and subsequently treating the titanate compound in aqueous solution of ammonium compound or amine compound (Patent Document 1 to 5). For a coating method with the titanium oxide nanosheets, super-thin film methods wherein the super-thin film is layered by alternately immersing a base material into the solution of cationic polymer and solution of nanosheets (Patent Document 6 to 9), anatase type or rutile type titanium oxide methods wherein these types of titanium oxide is heated so as to obtain an anatase type or rutile type titanium oxide film (Patent Document 6 and 10), or a film forming method wherein layers are formed according to Langmuir-Blodgett method (BL method) (Patent Document 11) are known.    Patent Document 1: Japanese Patent No. 2671949    Patent Document 2: Japanese Patent No. 2824506    Patent Document 3: Japanese Patent No. 2968440    Patent Document 4: Japanese Patent No. 2979132    Patent Document 5: Japanese Patent No. 3232306    Patent Document 6: Japanese Patent No. 3505574    Patent Document 7: Japanese Patent No. 3513589    Patent Document 8: Unexamined Japanese Patent Publication No. 2004-130429    Patent Document 9: Unexamined Japanese Patent Publication No. 2004-25568    Patent Document 10: Unexamined Japanese Patent Publication No. 2004-238226    Patent Document 11: Unexamined Japanese Patent Publication No. 2003-321222